Cam follower arm for an internal combustion engine

Abstract

A valve train in an internal combustion engine, and a method of adjusting the valve timing setting of a valve in such a valve train, are disclosed. In one embodiment, the present invention relates to an engine that includes a crankcase with a cylinder, a valve, a push rod, and a rocker arm supported by the crankcase and coupling the valve to the push rod. The internal combustion engine further includes a cam rotatably supported by the crankcase, and a cam follower arm having first and second ends and, proximate the second end, having bottom and top surfaces. The cam follower arm is rotatably supported by the crankcase about a pivot point proximate the first end. The bottom surface proximate the second end slidingly interfaces the cam, and the top surface proximate the second end interfaces the push rod.

1. An internal combustion engine comprising:
 a crankcase including a cylinder; 
 a first valve; 
 a first push rod; 
 a first rocker arm supported by the crankcase and coupling the first valve to the first push rod; 
 a first cam rotatably supported by the crankcase; and 
 a first cam follower arm having first and second ends and, at an end region proximate the second end, having bottom and top surfaces, 
 wherein the first cam follower arm is rotatably supported by the crankcase about a first pivot point proximate the first end, 
 wherein the bottom surface slidingly interfaces the first cam, and 
 wherein the top surface interfaces the first push rod, 
 whereby interaction of the first cam follower arm with both the first cam and the first push rod only occurs at the end region of the first cam follower arm and not within an intermediate region between the first end and the end region of the first cam follower arm. 
 
     
     
       2. The internal combustion engine of  claim 1 , wherein the first cam follower arm includes a shoe proximate the second end, wherein the shoe includes the bottom surface and the top surface. 
     
     
       3. The internal combustion engine of  claim 2 , wherein the bottom surface of the shoe has a substantially convex shape, and the top surface of the shoe has a substantially concave shape. 
     
     
       4. The internal combustion engine of  claim 3 , wherein the top surface of the shoe includes a dimple for receiving the first push rod. 
     
     
       5. The internal combustion engine of  claim 3 , wherein the first push rod is guided to experience linear movement by a retaining hole drilled within the crankcase so that the first push rod remains in contact with the shoe. 
     
     
       6. The internal combustion engine of  claim 3 , wherein the first cam follower arm is manufactured from sheet metal and includes an arm portion extending from the first end to the second end, and wherein the shoe is coupled to and substantially perpendicular to the arm portion. 
     
     
       7. The internal combustion engine of  claim 1 , wherein the first cam follower arm is rotatably supported about the first pivot point by way of a first bolt that extends from the first cam follower arm into a first hole in the crankcase. 
     
     
       8. The internal combustion engine of  claim 7 , wherein the crankcase includes a second hole, wherein the first cam follower arm can be repositioned so that the first cam follower arm is rotatably supported about a second pivot point by way of the first bolt extending through the second hole. 
     
     
       9. The internal combustion engine of  claim 7 , wherein the first hole is a curved slot, and wherein the first bolt can be repositioned along the curved slot so that the cam follower arm is rotatably supported by the crankcase at a plurality of different pivot points. 
     
     
       10. The internal combustion engine of  claim 1 , wherein the first cam follower arm can be repositioned on the crankcase so that the first cam follower arm is rotatably supported proximate the first end about at least one additional pivot point. 
     
     
       11. The internal combustion engine of  claim 10 , wherein the repositioning of the first cam follower arm results in a change in timing of the operation of the first valve. 
     
     
       12. The internal combustion engine of  claim 10 , wherein the first cam follower arm is repositioned by way of one of a manual operation and a mechanical operation. 
     
     
       13. The internal combustion engine of  claim 12 , wherein the first cam follower arm is repositioned by way of the mechanical operation, and wherein the first cam follower arm is repositioned in response the operation of a centrifugal governor supported by the engine. 
     
     
       14. The internal combustion engine of  claim 1 , further comprising a crankshaft interfacing a first gear that is coupled to the first cam, wherein rotation of the crankshaft causes the first gear and consequently the first cam to rotate, and wherein a timing of the operation of the first valve can be modified by adjusting the relative rotational positioning of the first gear with respect to the crankshaft, and further modified by adjusting the positioning of the first cam follower arm. 
     
     
       15. The internal combustion engine of  claim 1 , further comprising
 a second valve; 
 a second push rod; 
 a second rocker arm supported by the crankcase and coupling the second valve to the second push rod; 
 a second cam rotatably supported by the crankcase; and 
 a second cam follower arm having third and fourth ends and, proximate the fourth end, having lower and upper surfaces, 
 wherein the second cam follower arm is rotatably supported by the crankcase about a second pivot point proximate the third end, 
 wherein the lower surface proximate the fourth end interfaces the second cam, and 
 wherein the upper surface proximate the fourth end interfaces the second push rod. 
 
     
     
       16. An engine comprising:
 a cam; 
 a cam follower arm in contact with the cam, wherein the cam follower arm includes a first end and the cam follower arm is configured to pivot around a pivot point proximate the first end, and the cam follower arm further includes a second end and the cam follower arm is configured to interface a cam proximate the second end; 
 a valve, a rocker arm and a push rod, the rocker arm and the push rod linking the valve to the cam follower arm; 
 a crankcase having an elongated slot; and 
 a coupling element that rotatably couples the cam follower arm to the crankcase, 
 wherein the coupling element extends through the elongated slot and is capable of being moved to a variety of locations within the elongated slot such that the pivot point moves with respect to the crankcase and moving of the coupling element provides for fine adjustments in valve timing, and gross adjustments in the valve timing can be achieved by varying a rotational position of a first gear associated with the cam in relation to an additional gear that drives the first gear; 
 whereby the cam follower arm can be adjusted in its position relative to the crankcase so as to vary the interaction of the cam follower arm with the cam. 
 
     
     
       17. The engine of  claim 16 , wherein the engine further includes a mechanism that automatically moves the coupling element to different ones of the locations during engine operation.